I've been trying my hand at assembly/machine code going through the mastering machine code book (or at least the updated web version of it) here:
http://www.users.waitrose.com/~thunor/m ... ter14.html
I've been using the assembler pasmo on my linux (ubuntu) laptop.
I can actually run the game, and it prints the "breakout" screen, and even shoots the ball at the bricks. At this point the game freezes having accumulated a single point. Am actually quite pleased to have got this far, but would be cool to figure out what might be going wrong
Can anyone see where I've gone wrong? Have attached a debug output as well to compare with the opcodes of the original, and apart from some different memory addresses for some vars (BALLINIT etc) the opcodes look the same to me.
cheers
Daryn
Compiling:
Code: Select all
pasmo -v -d breakout.asm breakout.pCode: Select all
; mctemplate - a Sinclair ZX81 machine code template
; Copyright (C) 2010 Thunor <thunorsif_at_hotmail.com>
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <http://www.gnu.org/licenses/>.
; =====================================================================
; mctemplate 0.1.3
;
; Tabs are set to 8.
;
; See mctemplate.txt for assembling instructions and information.
; =====================================================================
; Sinclair character codes.
_SPC equ 0x00 ; " "
_DQT equ 0x0b ; "
_PND equ 0x0c ; £
_DLR equ 0x0d ; $
_CLN equ 0x0e ; :
_QMK equ 0x0f ; ?
_OBR equ 0x10 ; (
_CBR equ 0x11 ; )
_GTH equ 0x12 ; >
_LTH equ 0x13 ; <
_EQU equ 0x14 ; =
_PLS equ 0x15 ; +
_MNS equ 0x16 ; -
_ASK equ 0x17 ; *
_SLS equ 0x18 ; /
_SMC equ 0x19 ; ;
_CMA equ 0x1a ; ,
_FST equ 0x1b ; .
_0 equ 0x1c
_1 equ 0x1d
_2 equ 0x1e
_3 equ 0x1f
_4 equ 0x20
_5 equ 0x21
_6 equ 0x22
_7 equ 0x23
_8 equ 0x24
_9 equ 0x25
_A equ 0x26
_B equ 0x27
_C equ 0x28
_D equ 0x29
_E equ 0x2a
_F equ 0x2b
_G equ 0x2c
_H equ 0x2d
_I equ 0x2e
_J equ 0x2f
_K equ 0x30
_L equ 0x31
_M equ 0x32
_N equ 0x33
_O equ 0x34
_P equ 0x35
_Q equ 0x36
_R equ 0x37
_S equ 0x38
_T equ 0x39
_U equ 0x3a
_V equ 0x3b
_W equ 0x3c
_X equ 0x3d
_Y equ 0x3e
_Z equ 0x3f
; Inverse equivalents of the above.
_SPCV equ _SPC+0x80 ; [ ]
_DQTV equ _DQT+0x80 ; ["]
_PNDV equ _PND+0x80 ; [£]
_DLRV equ _DLR+0x80 ; [$]
_CLNV equ _CLN+0x80 ; [:]
_QMKV equ _QMK+0x80 ; [?]
_OBRV equ _OBR+0x80 ; [(]
_CBRV equ _CBR+0x80 ; [)]
_GTHV equ _GTH+0x80 ; [>]
_LTHV equ _LTH+0x80 ; [<]
_EQUV equ _EQU+0x80 ; [=]
_PLSV equ _PLS+0x80 ; [+]
_MNSV equ _MNS+0x80 ; [-]
_ASKV equ _ASK+0x80 ; [*]
_SLSV equ _SLS+0x80 ; [/]
_SMCV equ _SMC+0x80 ; [;]
_CMAV equ _CMA+0x80 ; [,]
_FSTV equ _FST+0x80 ; [.]
_0V equ _0+0x80
_1V equ _1+0x80
_2V equ _2+0x80
_3V equ _3+0x80
_4V equ _4+0x80
_5V equ _5+0x80
_6V equ _6+0x80
_7V equ _7+0x80
_8V equ _8+0x80
_9V equ _9+0x80
_AV equ _A+0x80
_BV equ _B+0x80
_CV equ _C+0x80
_DV equ _D+0x80
_EV equ _E+0x80
_FV equ _F+0x80
_GV equ _G+0x80
_HV equ _H+0x80
_IV equ _I+0x80
_JV equ _J+0x80
_KV equ _K+0x80
_LV equ _L+0x80
_MV equ _M+0x80
_NV equ _N+0x80
_OV equ _O+0x80
_PV equ _P+0x80
_QV equ _Q+0x80
_RV equ _R+0x80
_SV equ _S+0x80
_TV equ _T+0x80
_UV equ _U+0x80
_VV equ _V+0x80
_WV equ _W+0x80
_XV equ _X+0x80
_YV equ _Y+0x80
_ZV equ _Z+0x80
_NL equ 0x76
_VAL equ 0xc5
_INT equ 0xcf
_USR equ 0xd4
_NOT equ 0xd7
_PWR equ 0xd8 ; **
_THEN equ 0xde
_STOP equ 0xe3
_REM equ 0xea
_LET equ 0xf1
_PRINT equ 0xf5
_RUN equ 0xf7
_SAVE equ 0xf8
_RAND equ 0xf9
_IF equ 0xfa
; RST routines (a selection of).
ERROR equ 0x08 ; Follow with a byte error code -1.
PRINT_CHAR equ 0x10 ; regA contains the char.
; ROM routines (a selection of).
KEYB_SCAN equ 0x02bb
KEYB_DECODE equ 0x07bd
; Start of the system variables area.
ERR_NR equ 0x4000
FLAGS equ 0x4001
ERR_SP equ 0x4002
RAMTOP equ 0x4004
MODE equ 0x4006
PPC equ 0x4007
p_start: org 0x4009
VERSN: defb 0
E_PPC: defw 20 ; BASIC line number of line with cursor.
D_FILE: defw display_file
DF_CC: defw display_file+1
VARS: defw variables
DEST: defw 0
E_LINE: defw edit_line
CH_ADD: defw p_end-1
X_PTR: defw 0
STKBOT: defw p_end
STKEND: defw p_end
BERG: defb 0
MEM: defw MEMBOT
SPARE1: defb 0
DF_SZ: defb 2 ; Number of lines in lower part of screen.
S_TOP: defw 10 ; BASIC line number of line at top of screen.
LAST_K: defw 0xffff
DB_ST: defb 0
MARGIN: defb 55 ; Blank lines above/below TV picture: US = 31, UK = 55.
NXTLIN: defw display_file ; Memory address of next program line to be executed.
OLDPPC: defw 0
FLAGX: defb 0
STRLEN: defw 0
T_ADDR: defw 0x0c8d
SEED: defw 0
FRAMES: defw 0 ; Updated once for every TV frame displayed.
COORDS: defw 0
PR_CC: defb 0xbc
S_POSN: defb 0x21,0x18
CDFLAG: defb 0x40
PRBUF: defs 0x20
defb _NL
MEMBOT: defs 0x1e
SPARE2: defw 0
; Start of the BASIC area for user programs.
basic_0001: defb 0,1 ; 1 REM
defw basic_0010-basic_0001-4
defb _REM
; Start of user machine code program
;BALLINIT: DEFW 0x3C
;SPEED: DEFW 0x46
;BALLPOS: DEFW 0x40
;DIRECTION: DEFW 0x44
;BATPOS: DEFW 0x42
BALLINIT: DEFW 0
SPEED: DEFW 0
BALLPOS: DEFW 0
DIRECTION: DEFW 0
BATPOS: DEFW 0
mem_16514: JP BREAKOUT
; undefined subs
; undefined subs
TABLESTART: DEFW 0x0020,0x0022
DEFW 0xFFE0,0xFFDE
BREAKOUT: LD HL,(D_FILE) ;Load all of the bricks into
LD DE,0x0085 ;position.
ADD HL,DE
LD BC,0x8080 ;B is the number of bricks, C is a
NXBRK: INC HL ;constant used quite frequently in
LD A,(HL) ;this section.
CP 0x76
JR Z,NXBRK
LD (HL),0x08
DJNZ NXBRK
LD HL,(D_FILE) ;Put top wall in position.
LD B,0x1E ;This part puts in the first thirty
NXBL: INC HL ;blocks.
LD (HL),C
DJNZ NXBL
INC HL
LD (HL),0x9C ;The current score -zero - is
INC HL ;entered.
LD (HL),C ;The last block is set in place.
INC HL
INC HL
LD DE,0x001F ;DE is one more than the number of
LD B,0x17 ;spaces between the walls.
SIDES: LD (HL),C ;Both side walls are loaded into
ADD HL,DE ;position.
LD (HL),C
INC HL
INC HL
DJNZ SIDES
LD B,0x20 ;Now the base-line is drawn in.
BASE: LD (HL),0x1B
INC HL
DJNZ BASE
LD DE,0xFEFC ;This is the displacement from
;the current print position to
;the ball's starting point.
ADD HL,DE ;Locate this starting point.
LD (BALLINIT),HL ;Store it.
LD HL,0x0900 ;This is the initial speed.
LD (SPEED),HL ;Store it.
RESTART: LD HL,(BALLINIT) ;Change the starting
INC HL ;position of the ball.
LD (BALLINIT),HL
LD (BALLPOS),HL ;Start the ball here.
LD (HL),0x34 ;Print the ball.
LD HL,0xFFE0 ;Set the initial direction.
LD (DIRECTION),HL
LD A,(SPEED) ;Increase the speed.
DEC A
RET Z ;Return to BASIC if lives have
LD (SPEED),A ;run out.
LD HL,(D_FILE) ;Reprint the bat in its
LD DE,0x02B7 ;starting position.
ADD HL,DE
LD (HL),0x00
LD A,0x03 ;A contains the bat symbol.
INC HL
LD (HL),A
INC HL
LD (HL),A
INC HL
LD (HL),A
LD (BATPOS),HL ;Store the initial bat
INC HL ;position (this is the
LD (HL),A ;position of the centre of the
INC HL ;bat).
LD (HL),A
LD B,0x18 ;Now erase the rest of the
ERASE: INC HL ;row, in case a previous bat
LD (HL),0x00 ;symbol remains there.
DJNZ ERASE
LD HL,0x0000 ;Set a very long delay, for
JR DELAY ;the player to recover for the
; next ball.
LOOP: LD HL,(SPEED) ;This is a short delay loop
DELAY: DEC HL ;which controls the speed of
LD A,H ;the game.
OR L
JR NZ,DELAY
INC B ;The ball is only moved every
BIT 0x0,B ;other time round the loop, so
JR NZ,MOVEBAT ;that the bat moves twice as
;fast as the ball.
MOVEBALL: LD HL,(BALLPOS) ;Current ball position is found.
LD (HL),0x00 ;Erase the ball.
LD DE,(DIRECTION) ;Find next position of the ball.
ADD HL,DE
LD A,(HL) ;Find the contents of this new
CP 0x1B ;position.
JR Z,RESTART ;Has the ball hit the base?
LD C,A ;Start next ball if so.
AND 0xF7
JR NZ,DONTMOVE ;Only reprint the ball if the
LD (HL),0x34 ;new position is either empty
LD (BALLPOS),HL ;or contains a brick.
DONTMOVE: OR C ;Retrieve previous contents.
JR Z,MOVEBAT ;Change direction if not a
PUSH HL ;space.
LD HL,(SEED) ;Generate new direction at
LD D,H ;random.
LD E,L
ADD HL,HL
ADD HL,HL
ADD HL,DE
ADD HL,HL
ADD HL,HL
ADD HL,HL
ADD HL,DE
LD (SEED),HL
LD A,H ;Choose this direction from a
AND 0x06 ;table.
ADD A,TABLESTART
LD L,A
LD H,TABLESTART
LD E,(HL)
INC HL
LD D,(HL)
LD (DIRECTION),DE
POP HL
LD A,C ;If the contents of the square
CP 0x08 ;is not a brick, then move
JR NZ,MOVEBALL ;again.
LD HL,(D_FILE) ;Having established that a
LD DE,0x001F ;brick has been hit, the score
ADD HL,DE ;is increased by one.
CARRY: LD A,(HL)
CP 0x80
JR NZ,DIGIT
LD A,0x9C
DIGIT: INC A
CP 0xA6
JR NZ,INCREASED
LD (HL),0x9C
DEC HL
JR CARRY
INCREASED: LD (HL),A
MOVEBAT: PUSH BC ;Preserve the value of B.
CALL KEYB_SCAN ;Scan the keyboard.
POP BC
LD A,L
CPL
PUSH AF ;Stack contains a value
AND 0x0F ;corresponding to the key pressed.
JR Z,NOTLEFT ;If the player moves left....
LD HL,(BATPOS) ;Locate the bat.
DEC HL
DEC HL
DEC HL
LD A,(HL) ;Is there a wall to our left?
CP 0x80 ;If so, don't move.
JR Z,CYCLE1
LD (HL),0x03 ;Extend the bat to the left.
INC HL
INC HL
LD (BATPOS),HL ;Store new bat position.
INC HL
INC HL
INC HL
LD (HL),0x00 ;Decrease bat to the right.
NOTLEFT: POP AF
AND 0xF0
JR Z,CYCLE2 ;If the player moves right....
LD HL,(BATPOS)
INC HL
INC HL
INC HL
LD A,(HL) ;Is there a wall to the right?
CP 0x80 ;If so, don't move.
JR Z,CYCLE2
LD (HL),0x03 ;Extend the bat to the right.
DEC HL
DEC HL
LD (BATPOS),HL ;Store new bat position.
DEC HL
DEC HL
DEC HL
LD (HL),0x00 ;Decrease bat to the left.
PUSH HL ;Same for next time round.
CYCLE1: POP HL
CYCLE2: JP LOOP
; End of user machine code program ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
defb _NL
basic_0010: defb 0,10 ; 10 RAND VAL "USR 16514"
defw basic_0020-basic_0010-4
defb _RAND,_VAL,_DQT,_USR,_1,_6,_5,_1,_4,_DQT
defb _NL
basic_0020: defb 0,20 ; 20 REM ** TYPE RUN **
defw basic_end-basic_0020-4
defb _REM,_PWR,_SPC,_T,_Y,_P,_E,_RUN,_PWR
defb _NL
basic_end:
; Start of the display file (synonymous with video memory).
; Compressed for <= 3k RAM.
;display_file: defb _NL
; defb _NL,_NL,_NL,_NL,_NL,_NL,_NL,_NL
; defb _NL,_NL,_NL,_NL,_NL,_NL,_NL,_NL
; defb _NL,_NL,_NL,_NL,_NL,_NL,_NL,_NL
; Expanded for > 3k RAM.
display_file: defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
defs 32
defb _NL
; Start of the variables area used by BASIC.
variables: defb 0x80
; Start of the edit line used by BASIC.
edit_line:
p_end: end